Polyaxial bone anchor with pop-on shank, friction fit retainer and winged insert

ABSTRACT

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A down-loadable compression insert with tool receiving arm extensions, a down-loadable friction fit split retaining ring and an up-loadable shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/506,365, filed Apr. 13, 2012, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/517,088 filed Apr. 13, 2011,both applications are incorporated by reference herein. This applicationis also an continuation-in-part of U.S. patent application Ser. No.13/373,289, filed Nov. 9, 2011 that claims the benefit of U.S.Provisional Patent Application Ser. No. 61/456,649 filed Nov. 10, 2010and Provisional Patent Application Ser. No. 61/460,234 filed Dec. 29,2010, all of which are incorporated by reference herein. Thisapplication is also a continuation-in-part of U.S. patent applicationSer. No. 12/924,802 filed Oct. 5, 2010 that claims the benefit of thefollowing U.S. Provisional Patent Application Ser. Nos. 61/278,240,filed Oct. 5, 2009; 61/336,911, filed Jan. 28, 2010; 61/343,737 filedMay 3, 2010; 61/395,564 filed May 14, 2010; 61/395,752 filed May 17,2010; 61/396,390 filed May 26, 2010; 61/398,807 filed Jul. 1, 2010;61/400,504 filed Jul. 28, 2010; 61/402,959 filed Sep. 8, 2010;61/403,696 filed Sep. 20, 2010; and 61/403,915 filed Sep. 23, 2010, allof which are incorporated by reference herein. This application is alsoa continuation-in-part of U.S. patent application Ser. No. 12/802,849filed Jun. 15, 2010 that claims the benefit of the following U.S.Provisional Patent Application Ser. Nos. 61/268,708 filed Jun. 15, 2009;61/270,754, filed Jul. 13, 2009; 61/336,911 filed Jan. 28, 2010;61/395,564 filed May 14, 2010; 61/395,752 filed May 17, 2010; and61/396,390 filed May 26, 2010, all of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to polyaxial bone screws for use inbone surgery, particularly spinal surgery and particularly to suchscrews with compression or pressure inserts and expansion-only splitretainers to snap over, capture and retain the bone screw shank head inthe receiver member assembly and later fix the bone screw shank withrespect to the receiver assembly.

Bone screws are utilized in many types of spinal surgery in order tosecure various implants to vertebrae along the spinal column for thepurpose of stabilizing and/or adjusting spinal alignment. Although bothclosed-ended and open-ended bone screws are known, open-ended screws areparticularly well suited for connections to rods and connector arms,because such rods or arms do not need to be passed through a closedbore, but rather can be laid or urged into an open channel within areceiver or head of such a screw. Generally, the screws must be insertedinto the bone as an integral unit along with the head, or as apreassembled unit in the form of a shank and pivotal receiver, such as apolyaxial bone screw assembly.

Typical open-ended bone screws include a threaded shank with a pair ofparallel projecting branches or arms which form a yoke with a U-shapedslot or channel to receive a rod. Hooks and other types of connectors,as are used in spinal fixation techniques, may also include similar openends for receiving rods or portions of other fixation and stabilizationstructure.

A common approach for providing vertebral column support is to implantbone screws into certain bones which then in turn support a longitudinalstructure such as a rod, or are supported by such a rod. Bone screws ofthis type may have a fixed head or receiver relative to a shank thereof,or may be of a polyaxial screw nature. In the fixed bone screws, the rodreceiver head cannot be moved relative to the shank and the rod must befavorably positioned in order for it to be placed within the receiverhead. This is sometimes very difficult or impossible to do. Therefore,polyaxial bone screws are commonly preferred. Open-ended polyaxial bonescrews typically allow for a loose or floppy rotation of the head orreceiver about the shank until a desired rotational position of thereceiver is achieved by fixing such position relative to the shankduring a final stage of a medical procedure when a rod or otherlongitudinal connecting member is inserted into the receiver, followedby a locking screw or other closure. This floppy feature can be, in somecases, undesirable and make the procedure more difficult. Also, it isoften desirable to insert the bone screw shank separate from thereceiver or head due to its bulk which can get in the way of what thesurgeon needs to do. Such screws that allow for this capability aresometimes referred to as modular polyaxial screws.

With specific reference to modular snap-on or pop-on polyaxial pediclescrew systems having shank receiver assemblies, the prior art has shownand taught the concept of the receiver and certain retainer partsforming an assembly wherein a contractile locking engagement between theparts is created to fix the shank head with respect to the receiver andretainer. The receiver and shank head retainer assemblies in the priorart have included a slotted contractile retainer ring and/or a lowerpressure slotted insert with an expansion and contraction collet-type ofstructure having contractile locking engagement for the shank head dueto direct contact between the retainer and/or the collet structure withthe receiver resulting in contraction of the slotted retainer ringand/or the collet-type structure of the insert against the shank head.The receiver and slotted insert have generally included tapered lockingengagement surfaces.

The prior art for modular polyaxial screw assemblies has also shown andtaught that the contact surfaces on the outside of the slotted colletand/or retainer and the inside of the receiver, in addition to beingtapered, can be conical, radiused, spherical, curvate, multi-curvate,rounded, as well as other configurations to create a contractile type oflocking engagement for the shank head with respect to the receiver.

In addition, the prior art for modular polyaxial screw assemblies hasshown and taught that the shank head can both enter and escape from acollet-like structure on the insert or from the retainer when the insertor retainer is in the up position and within an expansion recess orchamber of the receiver. This is the case unless the slotted insertand/or the slotted retainer are blocked or constrained from being ableto be pushed or manipulated back up into receiver bore or cavity, orunless the screw assemblies are otherwise uniquely configured to preventthis from happening.

SUMMARY OF THE INVENTION

The present invention differentiates from the prior art by not allowingthe receiver to be removed from the shank head once the parts aresnapped-on and connected. This is true even if the retainer can go backup into the expansion chamber. This approach or design has been found tobe more secure and to provide more resistance to pull-out forcescompared to the prior art for modular polyaxial screw designs.Collect-like structures extending downwardly from lower pressureinserts, when used in modular polyaxial screw designs, as shown in theprior art, have been found to be somewhat weak with respect to pull-outforces encountered during some spinal reduction procedures. The presentinvention is designed to solve these problems.

The present invention also differentiates from all of the prior art byproviding a split retainer ring with an inner radiused or partiallyspherical surface having a smaller radius than the shank upper portionthat does not frictionally engage and thus does not participate in thelocking engagement for the shank head with respect to the receiver.Rather upper and/or lower edges or surfaces that partially define thespherical surface frictionally engage the shank head to provide adesired non-floppy engagement, the angle of the shank with respect tothe retainer being manipulatable with some force. In addition, theretainer ring itself for the present invention is uniquely characterizedby a base portion providing expansion to receive and capture the shankhead and then having only expansion (not contraction) locking engagementbetween the shank head and the retainer ring base and between theretainer ring base and horizontal and vertical loading surfaces near abottom opening of the receiver.

The expansion-only retainer ring base portion in the present inventionis positioned entirely below the shank head hemisphere in the receiverand can be a stronger, more substantial structure to resist larger pullout forces on the assembly. The retainer ring base can also be bettersupported on a generally horizontal loading surface near the loweropening in the bottom of the receiver. This design has been found to bestronger and more secure when compared to that of the prior art whichuses some type of contractile locking engagement between the parts, asdescribed above; and, again, once assembled it cannot be disassembled.

Thus, a polyaxial bone screw assembly according to the inventionincludes a shank having an integral upper portion or integral radiusedor spherical head and a body for fixation to a bone; a separate receiverdefining an upper open channel, a central bore, a lower cavity and alower opening; a top drop and turn in place lower compression insert;and a friction fit resilient expansion-only split retainer for capturingthe shank head in the receiver lower cavity, the shank head beingfrictionally engaged with, but still movable in a non-floppy manner withrespect to the friction fit retainer and the receiver prior to lockingof the shank into a desired configuration. The compression insertfurther includes winged arm portions that extend outwardly throughapertures in the receiver arms, providing for manipulation and seatingof the retainer with respect to the receiver, and if desired,independent temporary locking of the insert against the shank. The shankis finally locked into a fixed position relative to the receiver byfrictional engagement between the insert and a lower split ring-likeportion of the retainer, as described previously, due to a downwardforce placed on the compression insert by a closure top pressing on arod, or other longitudinal connecting member, captured within thereceiver bore and channel. In the illustrated embodiments, retainers andcompression inserts are downloaded into the receiver, but uploadedembodiments are also foreseen. The shank head can be positioned into thereceiver lower cavity at the lower opening thereof prior to or afterinsertion of the shank into bone. In some embodiments, the compressioninsert may include a lock and release feature for independent locking ofthe polyaxial mechanism so the screw can be used like a fixed monoaxialscrew. Also, in some embodiments the shank can be cannulated forminimally invasive surgery applications. The receiver can have crimptabs, but is devoid of any type of spring tabs or collet-likestructures. The lower pressure insert and/or the retainer are bothdevoid of any type of receiver-retainer contractile locking engagementswith respect to the shank head, and again the receiver is devoid of anyspring-tab like members. The retainer can also have upwardly extendingspring tabs which are deployed into openings in the receiver cavity sothat the retainer and captured shank head are stabilized and retained inthe region of the receiver locking chamber once they enter into thislower portion of the receiver cavity. In this way, the shank head andretainer are constrained and cannot go back up into the receiver cavity.

Again, a pre-assembled receiver, compression insert and friction fitsplit retainer may be “pushed-on”, “snapped-on” or “popped-on” to theshank head prior to or after implantation of the shank into a vertebra.Such a “snapping on” procedure includes the steps of uploading the shankhead into the receiver lower opening, the shank head pressing againstthe base portion of the split retainer ring and expanding the resilientlower open retainer portion out into an expansion portion or chamber ofthe receiver cavity followed by an elastic return of the retainer backto a nominal or near nominal shape thereof after the hemisphere of theshank head or upper portion passes through the lower ring-like portionof the retainer. The shank head enters into friction fit engagement withportions of the retainer, defined at least in part, by an inner curvedsurface or edge, such surface or edge having a radius smaller than aradius of the shank head surface being engaged by the retainer. Theretainer snapping onto the shank head as the retainer returns to aneutral or close to neutral orientation, providing a non-floppyconnection between the retainer and the shank head. In the illustratedembodiment, when the shank is ultimately locked between the compressioninsert and the lower portion of the retainer, only a lower surfacedefining the retainer radiused surface is required for lockingengagement with the shank head. The final fixation occurs as a result ofa locking expansion-type of contact between the shank head and the lowerportion of the split retainer and an expansion-type of non-taperedlocking engagement between the lower portion of the retainer ring andthe locking chamber in the lower portion of the receiver cavity. Theretainer can expand more in the upper portion or expansion chamber ofthe receiver cavity to allow the shank head to pass through, but hasrestricted expansion to retain the shank head when the retainer lowerring portion is against the locking chamber surfaces in the lowerportion of the receiver cavity and the shank head is forced down againstthe retainer ring during final locking. In some embodiments, when thepolyaxial mechanism is locked, the pressure or compression insert isforced or wedged against a surface of the receiver resulting in aninterference locking engagement, allowing for adjustment or removal ofthe rod or other connecting member without loss of a desired angularrelationship between the shank and the receiver. This independentlocking feature allows the polyaxial screw to function like a fixedmonoaxial screw.

The lower pressure insert may also be configured to be independentlylocked by a tool or instrument, thereby allowing the pop-on polyaxialscrew to be distracted, compressed and/or rotated along and around therod to provide for improved spinal correction techniques. Such a toolengages the receiver from the sides and then engages outwardly extendingwinged arms of the insert to force or wedge the insert down into alocked position within the receiver. With the tool still in place andthe correction maintained, the rod is then locked within the receiverchannel by a closure top followed by removal of the tool. This processmay involve multiple screws all being manipulated simultaneously withmultiple tools to achieve the desired correction.

It is noted that once the shank head is captured by the retainer ringand the retainer and head are moved down into the locking chamber regionof the receiver cavity, retainer spring tabs are deployed outwardlystabilizing the retainer so that the retainer cannot go back up into thereceiver cavity. This spring tab deployment also creates good rotationalstability between the retainer and receiver and provides for anadditional rotational friction fit between the shank head and thereceiver itself since the retainer cannot axially rotate in thereceiver. In this position, the retainer is fully constrained in thereceiver with respect to translation, rotation and pivot.

Objects of the invention further include providing apparatus and methodsthat are easy to use and especially adapted for the intended use thereofand wherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded front elevational view of a polyaxial bone screwassembly according to the present invention including a shank, areceiver, an open friction fit expansion-only retainer and a top dropand turn in place lower compression insert, further shown with a portionof a longitudinal connecting member in the form of a rod and a closuretop.

FIG. 2 is an enlarged top plan view of the shank of FIG. 1.

FIG. 3 is a reduced cross-sectional view taken along the line 3-3 ofFIG. 2.

FIG. 4 is an enlarged side elevational view of the receiver of FIG. 1.

FIG. 5 is an enlarged perspective view of the receiver of FIG. 4.

FIG. 6 is an enlarged top plan view of the receiver of FIG. 4.

FIG. 7 is an enlarged bottom plan view of the receiver of FIG. 4.

FIG. 8 is another perspective view of the receiver of FIG. 4.

FIG. 9 is an enlarged cross-sectional view taken along the line 9-9 ofFIG. 6.

FIG. 10 is an enlarged cross-sectional view taken along the line 10-10of FIG. 6.

FIG. 11 is an enlarged perspective view of the retainer of FIG. 1.

FIG. 12 is another perspective view of the retainer of FIG. 11.

FIG. 13 is another reduced perspective view of the retainer of FIG. 11.

FIG. 14 is a top plan view of the retainer of FIG. 11.

FIG. 15 is a bottom plan view of the retainer of FIG. 11.

FIG. 16 is a cross-sectional view taken along the line 16-16 of FIG. 14.

FIG. 17 is a cross-sectional view taken along the line 17-17 of FIG. 14.

FIG. 18 is an enlarged perspective view of the insert of FIG. 1.

FIG. 19 is a side elevational view of the insert of FIG. 18.

FIG. 20 is a bottom plan view of the insert of FIG. 18.

FIG. 21 is a top plan view of the insert of FIG. 18.

FIG. 22 is a cross-sectional view taken along the line 22-22 of FIG. 21.

FIG. 23 is a cross-sectional view taken along the line 23-23 of FIG. 21.

FIG. 24 is an enlarged front elevational view of the retainer andreceiver of FIG. 1 with portions of the receiver broken away to show thedetail thereof, the retainer being shown downloaded into the receiver(in phantom) to a partially inserted stage of assembly.

FIG. 25 is an enlarged front elevational view of the retainer andreceiver with portions broken away, similar to what is shown in FIG. 24,showing the retainer in a subsequent stage of assembly (someintermediate stages in phantom) and further showing the insert of FIG.1, in enlarged side elevation, just prior to being loaded into thereceiver.

FIG. 26 is a reduced front elevational view of the retainer and receiverwith portions broken away, similar to what is shown in FIG. 25, furthershowing the insert being downloaded into the receiver to a partiallyinserted stage of assembly.

FIG. 27 is a front elevational view with portions broken away, similarto FIG. 26, showing the insert being rotated within the receiver.

FIG. 28 is a perspective view, with portions broken away, of thereceiver, retainer and insert of FIG. 27, the insert fully rotated intoalignment with the receiver and further showing the receiver crimped tothe insert.

FIG. 29 is an enlarged side elevational view of the receiver, retainerand insert of FIG. 28, also showing the receiver crimped to the insert.

FIG. 30 is an enlarged front elevational view with portions broken away,showing a subsequent stage of assembly to that shown in FIG. 28 withretainer spring tab arms being pressed toward one another and theretainer being moved upwardly within the receiver.

FIG. 31 is an enlarged front elevational view with portions broken away,showing a subsequent stage of assembly to that shown in FIG. 30, showingthe retainer spring tab arms placed in a desired upward position withinthe receiver so that the retainer spring tabs push resiliently outwardlyagainst the receiver, holding the retainer against the receiver andkeeping the insert in an upward position during shipping.

FIG. 32 is a reduced front elevational view with portions broken away,similar to FIG. 31, and further showing the shank of FIG. 1 in partialfront elevation, the shank being in a first stage of assembly with thereceiver and retainer, a hemisphere of the shank head and a vertebraportion are both shown in phantom.

FIG. 33 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 32, showing the retainer lower portion inan expanded state about a mid-portion of the shank head.

FIG. 34 is a reduced and partial perspective view (the receiver beingcompletely removed) of the assembly as shown in FIG. 33.

FIG. 35 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 33, the spherical shank upper portion orhead shown fully captured by the retainer.

FIG. 36 is a partial front elevational view with portions broken away,similar to FIG. 35, the shank upper portion with attached retainer beingshown pulled down into a partially seated position within the lowerreceiver cavity, the retainer spring tabs in a substantially neutralstate, extending outwardly partially into receiver apertures.

FIG. 37 is a reduced and partial front elevational view with portionsbroken away, similar to FIG. 36, the insert being shown in a positiondropped down on the retainer spring tabs.

FIG. 38 is an enlarged and partial front elevational view with portionsbroken away, similar to FIG. 37, the retainer being shown pushed downinto a fully seated position within the lower receiver cavity bypressure being placed thereon from above onto the insert, the insertfurther pressing the retainer spring tabs outwardly into the receiverapertures.

FIG. 39 is an enlarged and partial front elevational view with portionsbroken away of all of the components shown in FIG. 1, the assembly ofFIG. 38 shown in an early stage of assembly with the rod and closuretop.

FIG. 40 is a partial front elevational view with portions broken away,similar to FIG. 39, shown in a final locking position.

FIG. 41 is a reduced and partial perspective view of the assembly ofFIG. 40, but with the shank shown disposed at about a twenty-five degree(caudad) angle with respect to the receiver.

FIG. 42 is a reduced and partial perspective view of the assembly ofFIG. 40, but with the shank shown disposed at about a twenty-five degree(medial) angle with respect to the receiver.

FIG. 43 is a partial front elevational view of the assembly as shown inFIG. 42 with portions broken away to show the detail thereof.

FIG. 44 is a reduced and partial perspective view of the assembly ofFIG. 40, but with the shank shown disposed at about a forty degree(medial) angle with respect to the receiver.

FIG. 45 is a partial front elevational view of the assembly as shown inFIG. 44 with portions broken away to show the detail thereof.

FIG. 46 is a reduced and partial perspective view of the assembly ofFIG. 40, but with the shank shown disposed at about a twenty-five degree(multi-plane) angle with respect to the receiver.

FIG. 47 is an enlarged perspective view of an alternative retaineraccording to the invention for use with the assembly of FIG. 1.

FIG. 48 is another enlarged perspective view of the retainer of FIG. 47.

FIG. 49 is an enlarged perspective view of another alternative retaineraccording to the invention for use with the assembly of FIG. 1.

FIG. 50 is another enlarged perspective view of the retainer of FIG. 49.

FIG. 51 is an enlarged perspective view of another alternative retaineraccording to the invention for use with the assembly of FIG. 1.

FIG. 52 is another enlarged perspective view of the retainer of FIG. 51.

FIG. 53 is an enlarged perspective view of another alternative retaineraccording to the invention for use with the assembly of FIG. 1.

FIG. 54 is another enlarged perspective view of the retainer of FIG. 53.

FIG. 55 is an enlarged front elevational view of an alternative insertaccording to the invention for use with the assembly of FIG. 1 havingouter independent lock-and-release surfaces and inner tool receivingslots.

FIG. 56 is a top plan view of the alternative insert of FIG. 55 with theinner tool receiving slots being shown in phantom.

FIG. 57 is a cross-sectional view taken along the line 57-57 of FIG. 56.

FIG. 58 is a cross-sectional view taken along the line 58-58 of FIG. 56.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

With reference to FIGS. 1-46, the reference number 1 generallyrepresents a polyaxial bone screw apparatus or assembly according to thepresent invention. The assembly 1 includes a shank 4, that furtherincludes a body 6 integral with an upwardly extending upper portion orhead structure 8; a receiver 10; a friction fit retainer 12, and acrown-like compression or pressure insert 14. The receiver 10, retainer12 and compression insert 14 are initially assembled and may be furtherassembled with the shank 4 either prior or subsequent to implantation ofthe shank body 6 into a vertebra 17, as will be described in greaterdetail below. FIGS. 1 and 39-40 further show a closure structure 18 forcapturing a longitudinal connecting member, for example, a rod 21 whichin turn engages the compression insert 14 that presses against the shankupper portion 8 into fixed frictional contact with the retainer 12, soas to capture, and fix the longitudinal connecting member 21 within thereceiver 10 and thus fix the member 21 relative to the vertebra 17. Thereceiver 10 and the shank 4 cooperate in such a manner that the receiver10 and the shank 4 can be secured at any of a plurality of angles,articulations or rotational alignments relative to one another andwithin a selected range of angles both from side to side and from frontto rear, to enable flexible or articulated engagement of the receiver 10with the shank 4 until both are locked or fixed relative to each othernear the end of an implantation procedure. The illustrated rod 21 ishard, stiff, non-elastic and cylindrical, having an outer cylindricalsurface 22. It is foreseen that in other embodiments, the rod 21 may beelastic, deformable and/or of different materials and cross-sectionalgeometries. In such cases, the closure top could deform the rod andpress directly on the insert 14.

The shank 4, best illustrated in FIGS. 1-3, is elongate, with the shankbody 6 having a helically wound bone implantable thread 24 (single ordual lead thread form and different thread types) extending from near aneck 26 located adjacent to the upper portion or head 8, to a tip 28 ofthe body 6 and extending radially outwardly therefrom. During use, thebody 6 utilizing the thread 24 for gripping and advancement is implantedinto the vertebra 17 leading with the tip 28 and driven down into thevertebra with an installation or driving tool (not shown), so as to beimplanted in the vertebra to a location at or near the neck 26, as morefully described in the paragraphs below. The shank 4 has an elongateaxis of rotation generally identified by the reference letter A.

The neck 26 extends axially upward from the shank body 6. The neck 26may be of the same or is typically of a slightly reduced radius ascompared to an adjacent upper end or top 32 of the body 6 where thethread 24 terminates. Further extending axially and outwardly from theneck 26 is the shank upper portion or head 8 that provides a connectiveor capture apparatus disposed at a distance from the upper end 32 andthus at a distance from the vertebra 17 when the body 6 is implanted insuch vertebra.

The shank upper portion 8 is configured for a pivotable connectionbetween the shank 4 and the retainer 12 and receiver 10 prior to fixingof the shank 4 in a desired position with respect to the receiver 10.The shank upper portion 8 has an outer, convex and substantiallyspherical surface 34 that extends outwardly and upwardly from the neck26 that in some embodiments terminates at a substantially planar top orrim surface 38. In the illustrated embodiment, a frusto-conical surface39 extends from the spherical surface 34 inwardly to the top surface 38,providing additional clearance during pivoting of the shank with respectto the receiver 10 and the insert 14. The spherical surface 34 has anouter radius configured for temporary frictional, non-floppy, slidingcooperation with one or more edges or surfaces of the retainer 12, aswell as ultimate frictional engagement with the insert 14 at an innerpartially spherical surface thereof, as will be discussed more fully inthe paragraphs below. The spherical surface 34 shown in the presentembodiment is substantially smooth, but in some embodiments may includea roughening or other surface treatment and is sized and shaped forcooperation and ultimate frictional engagement with the compressioninsert 14 as well as ultimate frictional engagement with a lowerring-like portion of the retainer 12. The shank spherical surface 34 islocked into place exclusively by the insert 14 and the retainer 12 lowerportion and not by inner surfaces defining the receiver cavity.

A counter sunk stepped or graduated annular seating surface or base 45partially defines an internal drive feature or imprint 46. In someembodiments of the invention, the surface 45 is substantially planar.The illustrated internal drive feature 46 is an aperture formed in thetop surface 38 and has a star shape designed to receive a tool (notshown) of an Allen wrench type, into the aperture for rotating anddriving the bone screw shank 4. It is foreseen that such an internaltool engagement structure may take a variety of tool-engaging forms andmay include one or more apertures of various shapes, such as a pair ofspaced apart apertures or a multi-lobular or hex-shaped aperture. Thegraduated seat or base surfaces 45 of the drive feature 46 are disposedsubstantially perpendicular to the axis A with the drive feature 46otherwise being coaxial with the axis A. As illustrated in FIGS. 2 and3, the drive seat 45 having beveled or stepped surfaces advantageouslyfurther enhances gripping with the driving tool. In operation, a drivingtool (not shown) is received in the internal drive feature 46, beingseated at the base 45 and engaging the faces of the drive feature 46 forboth driving and rotating the shank body 6 into the vertebra 17, eitherbefore the shank 4 is attached to the receiver 10 or after the shank 4is attached to the receiver 10, with the shank body 6 being driven intothe vertebra 17 with the driving tool extending into the receiver 10.

The shank 4 shown in the drawings is cannulated, having a small centralbore 50 extending an entire length of the shank 4 along the axis A. Thebore 50 is defined by an inner cylindrical wall of the shank 4 and has acircular opening at the shank tip 28 and an upper opening communicatingwith the external drive 46 at the driving seat 45. The bore 50 iscoaxial with the threaded body 6 and the upper portion 8. The bore 50provides a passage through the shank 4 interior for a length of wire(not shown) inserted into the vertebra 17 prior to the insertion of theshank body 6, the wire providing a guide for insertion of the shank body6 into the vertebra 17. It is foreseen that the shank could be solid andmade of different materials, including metal and non-metals.

To provide a biologically active interface with the bone, the threadedshank body 6 may be coated, perforated, made porous or otherwisetreated. The treatment may include, but is not limited to a plasma spraycoating or other type of coating of a metal or, for example, a calciumphosphate; or a roughening, perforation or indentation in the shanksurface, such as by sputtering, sand blasting or acid etching, thatallows for bony ingrowth or ongrowth. Certain metal coatings act as ascaffold for bone ingrowth. Bio-ceramic calcium phosphate coatingsinclude, but are not limited to: alpha-tri-calcium phosphate andbeta-tri-calcium phosphate (Ca₃(PO₄)₂, tetra-calcium phosphate(Ca₄P₂O₉), amorphous calcium phosphate and hydroxyapatite(Ca₁₀(PO₄)₆(OH)₂). Coating with hydroxyapatite, for example, isdesirable as hydroxyapatite is chemically similar to bone with respectto mineral content and has been identified as being bioactive and thusnot only supportive of bone ingrowth, but actively taking part in bonebonding.

With particular reference to FIGS. 1 and 4-10, the receiver 10 has agenerally U-shaped appearance with partially discontinuous and partiallycylindrical inner and outer profiles. The receiver 10 has an axis ofrotation B that is shown in FIG. 1 as being aligned with and the same asthe axis of rotation A of the shank 4, such orientation being desirable,but not required during assembly of the receiver 10 with the shank 4.After the receiver 10 is pivotally attached to the shank 4, eitherbefore or after the shank 4 is implanted in a vertebra 17, the axis B istypically disposed at an angle with respect to the axis A, as shown, forexample, in FIGS. 41-46.

The receiver 10 includes a substantially cylindrical base 60 defining abore or inner cavity, generally 61, the base 60 being integral with apair of opposed upstanding arms 62 forming a cradle and defining achannel 64 between the arms 62 with an upper opening, generally 66, anda U-shaped lower channel portion or seat 68, the channel 64 having awidth for operably snugly receiving the rod 21 or portion of anotherlongitudinal connector between the arms 62, the channel 64 communicatingwith the base cavity 61. Inner opposed substantially planar arm surfaces69 partially define the channel 64 directly above the seat 68 and arelocated on either side of each arm interior surface generally 70, thatincludes various inner cylindrical profiles, an upper one of which is apartial helically wound guide and advancement structure 72 locatedadjacent top surfaces 73 of each of the arms 62. In the illustratedembodiment, the guide and advancement structure 72 is a partialhelically wound interlocking flangeform configured to mate underrotation with a similar structure on the closure structure 18, asdescribed more fully below. However, it is foreseen that for certainembodiments of the invention, the guide and advancement structure 72could alternatively be a square-shaped thread, a buttress thread, areverse angle thread or other thread-like or non-thread-like helicallywound discontinuous advancement structures, for operably guiding underrotation and advancing the closure structure 18 downward between thearms 62, as well as eventual torquing when the closure structure 18abuts against the rod 21 or other longitudinal connecting member. It isforeseen that the arms 62 could have break-off extensions.

An opposed pair of vertically extending outer grooves, generally 74,running substantially parallel to the receiver axis B are centrallyformed in outer cylindrical surfaces 76 of the arms 62. Each groove 74runs centrally from the respective arm top surface 73 and terminates ata location spaced from a lower through aperture 77. Each aperture 77extends through the respective arm surface 77 to the respective innerarm surface 70. Each aperture 77 is located near or adjacent thereceiver base 60. A portion of each groove 74 also extends completelythrough the respective arm 62 and opens into the inner arm surface 70.Specifically, each groove 74 has an upper opening partially defined by apair of opposed surfaces 79 and 80 and a substantially planar outer wallsurface 81 extending between the surfaces 79 and 80. The planar wallsurface terminates at the top surface 73 and at a lower surface 82. Thelower surface 82 partially defines an open or through aperture portion83 of each groove, the lower surface 82 extending between to therespective inner arm surface 70. The opposed surfaces 79 and 80 aredisposed at an angle with respect to each other, forming the groove 74as a dovetail-like space for easily receiving an elongate tool (notshown) that enters into the groove 74 at the arm top surface 73 and iskept in close sliding contact with the surface 81 by the orientation ofthe surfaces 79 and 80 angling toward one another with the tool slidingalong the surface 81 and ultimately into contact with winged portions ofthe insert 14 that extend through the aperture 83 as will be describedin greater detail below. At the through aperture 83, the dovetailsurfaces 79 and 80 terminate at or near a generally u-shaped lowersurface 84, the surface 84 also sloping downwardly and outwardly towardthe outer arm surface 76 from a lower ledge 85 that partially definesthe through aperture 83 at the respective arm inner surface 70. Theledge 85 is spaced from and located directly below the wall 81. Betweenthe ledge 85 and the wall 81 and integral with each of the groovesurfaces 79 and 80 are opposed crimping walls or flat tabs 86 and 87that extend from the respective surfaces 79 and 80 at the inner armsurface 70 and are generally directed toward one another into thethrough aperture 83 space. The crimping walls or tabs 86 and 87 aresized and shaped for pressing or crimping some or all of the tabmaterial into grooves of the insert 14 to prohibit rotation andmisalignment of the insert 14 with respect to the receiver 10 as will bedescribed in greater detail below. In other embodiments of theinvention, other surfaces at or near the grooves 74 may be inwardlycrimped. The illustrated through apertures 77 located below the grooves74 are relatively narrow, each including a pair of opposed circularsegments 89 extending outwardly from the nearby groove 74, the segments89 being connected by upper and lower parallel walls, forming agenerally rectangular portion 90. The through apertures 77 are sized andshaped for receiving spring tab portions of the retainer 12 duringassembly and final operation that capture and retain the retainer 12within the receiver as shown, for example, in FIG. 25. It is foreseenthat in some embodiments of the invention, the apertures 77 will have anupper portion that is not a through-aperture, but rather a recessed wallof the receiver that allows for the spring tab portions to partiallyexpand into contact with such a recessed wall, but remain slightlycompressed to provide increased friction fit between the retainer andthe shank head during manipulation of the shank with respect to thereceiver. Then, during a final locking procedure, the spring tabportions will be further lowered to extend completely through a lowerthrough aperture area of the respective aperture 77.

The receiver 10 is a one-piece or integral structure and is devoid ofany spring tabs or collet-like structures. Preferably the insert and/orreceiver are configured with structure for blocking rotation of theinsert with respect to the receiver, such as the crimp walls 86 and 87,but allowing some up and down movement of the insert with respect to thereceiver during the assembly and implant procedure. Also formed in eachouter arm surface 76 near the top surface 73 is an undercut toolreceiving and engaging groove 91. Some or all of the apertures andgrooves described herein, including, but not limited to grooves 74,apertures 83, and grooves 91 may be used for holding the receiver 10during assembly with the insert 14, the retainer 12 and the shank 4;during the implantation of the shank body 6 into a vertebra when theshank is pre-assembled with the receiver 10; during assembly of the boneanchor assembly 1 with the rod 21 and the closure structure 18; andduring lock and release adjustment of alternative inserts according tothe invention with respect to the receiver 10, either into or out offrictional engagement with the inner surfaces of the receiver 10 as willbe described in greater detail below. It is foreseen that tool receivinggrooves or apertures may be configured in a variety of shapes and sizesand be disposed at other locations on the receiver arm 62 outer surfaces76 and/or inner surfaces 70 as well as the base 60 outer or innersurfaces.

Returning to the interior surface 70 of the receiver arms 62, locatedbelow the guide and advancement structure 72 is a discontinuouscylindrical surface 92 partially defining a run-out feature for theguide and advancement structure 72. The cylindrical surface 92 is sizedand shaped to receive an upper winged portion of the insert 14 as willbe described in greater detail below. Therefore, the surface 92 has adiameter greater than a greater diameter of the guide and advancementstructure 72. The illustrated receiver 10 further includes sloped,stepped or chamfered surfaces above and below the surface 92. Thesurface 92 is divided not only by the U-shaped channel 64, but also byeach of the through apertures 83, resulting in the surface 92 being infour sections. A lower partially sloping or stepped ledge 94 at the baseof the cylindrical surface 92 slopes downwardly toward the receiver base60 and then extends inwardly toward the axis B, the surface 94terminating at a discontinuous cylindrical surface 95. A discontinuousinwardly sloping surface or narrow ledge 96 is located below the surface95 and is adjacent another partially discontinuous cylindrical surface97. It is noted that in some embodiments of the invention, the surfaces95 and 97 are combined and form a single cylindrical surface. Thethrough aperture 83 extends through the surface 95 while the throughaperture 77 extends through the surface 97. In the illustratedembodiment, the aperture 77 is located and sized so that the slopingsurface 96 and a portion of the cylindrical surface 97 form a narrowinwardly facing projection or lip for temporary engagement with groovesformed in outwardly extending resilient spring tabs of the retainer 12as will be described in greater detail below. Portions of the surfaces95 are pressed into engagement with the insert 14 when the thin,deformable walls or tabs 86 and 87 are pressed toward the insert 14 aswill be described in greater detail below. A lower portion of thesurface 97 located between the arms 62 and below the U-shaped channelseating surface 68 terminates at a discontinuous annular surface orledge 98 disposed substantially perpendicular to the axis B, but couldbe oblique. The discontinuous surface 98 partially defines the basecavity 61. The surface 98 terminates at each of the through apertures77. A continuous cylindrical surface 99 is located below and adjacent tothe surface 98 and the apertures 77. The cylindrical surface 99 isoriented substantially parallel to the axis B and is sized and shaped toreceive an expanded portion of retainer 12. The surface 99 defines acircumferential recess that is sized and shaped to receive the retainer12 as it expands around the shank upper portion 8 as the shank 8 movesupwardly toward the channel 64 during assembly. It is foreseen that therecess could be tapered or conical in configuration. A cylindricalsurface 101 located below the cylindrical surface 99 is sized and shapedto closely receive and surround a lower portion of the retainer 12 whenthe retainer is in a reduced deployment position as shown in FIG. 39,for example. Thus, the cylindrical surface 101 has a diameter smallerthan the diameter of the cylindrical surface 99 that defines theexpansion area or expansion chamber for the retainer 12. The surface 101is joined or connected to the surface 99 by one or more beveled, curvedor conical surfaces 102. The surfaces 102 allow for sliding and nominalor deployment positioning of the retainer 12 into the space defined bythe surface 101 and ultimate seating of the retainer 12 on a lowersubstantially horizontal annular surface 104 located below and adjacentto the cylindrical surface 101. The surface 104 is orientedsubstantially perpendicular to the axis B.

Located below and adjacent to the annular seating surface 104 is anothersubstantially cylindrical surface 106 that communicates with a beveledor flared bottom opening surface 107, the surface 107 communicating withan exterior base surface 108 of the base 60, defining a lower opening,generally 110, into the base cavity 61 of the receiver 10. Formed in aportion of the base surface 108, as well as in portions of the surfaces107, 106, 104 and 101 is a curvate cut-out or cupped surface 109 locatedsubstantially centrally and directly below one of the arms 62. Asillustrated in FIGS. 44 and 45, for example, the cupped surface 109 issized and shaped for providing clearance for an increased angle ofarticulation between the shank 4 and the receiver 10 as will bedescribed in greater detail below.

With particular reference to FIGS. 1 and 11-17, the lower open or splitfriction fit retainer 12, that operates to capture the shank upperportion 8 within the receiver 10, has a central axis that isoperationally the same as the axis B associated with the receiver 10when the shank upper portion 8 and the retainer 12 are installed withinthe receiver 10. The retainer 12 includes a substantially cylindricaldiscontinuous body 116. Extending upwardly and outwardly from the body116, and integral thereto, are a pair of opposed spring arms or tabs118. The retainer ring 12 is made from a resilient material, such as astainless steel or titanium alloy, so that the retainer 12 body 116 maybe expanded and the tabs 118 of the retainer may be manipulated duringvarious steps of assembly as will be described in greater detail below.The retainer 12 has a central channel or hollow through bore, generally121, that passes entirely through the retainer 12 from tab 118 topsurfaces 122 to a bottom surface 124 of the retainer body 116. Surfacesthat define the channel or bore 121 at the body 116 include an innerlower frusto-conical surface 128 adjacent to the retainer body bottomsurface 124, a narrow substantially cylindrical surface 130 adjacent thefrusto-conical surface 128 and a discontinuous concave radiused orpartially spherical surface 132 located adjacent the cylindrical surface130, the surface 132 extending upwardly to an upper discontinuous edgeor rim surface 133 located between the spring tabs 118, each rim surface133 partially defined by a retainer body upper or top surface 134, thetop surface being substantially planar and discontinuous, disposedsubstantially parallel to the body bottom surface 124 and terminating ateach of the spring tabs 118 and at a slit, generally 136. The obtuseslit 136 creates a split or open ring retainer 12, the slit cuttingentirely through the retainer body 116. In some embodiments, such a slitmay run perpendicular to the surfaces 124 and 134. The slit 136 is forexpansion purposes only during pop-on or snap-on assembly with the shankhead 8. The retainer 12 base does not necessarily need to be contractedwhen loaded into the receiver 10, while the spring tabs 118 can be. Theillustrated inner radiused or partially spherical surface 132 has aradius that is smaller than the radius of the spherical shank surface34. The slit 136 is disposed at an obtuse angle with respect to the topsurface 134 and extends between the top surface 134 and a concavecut-out or cupped surface 138 formed in the body bottom surface 124. Theslit can be of different shapes and located in other locations. At eachof the spring tabs 118, the rim or edge 132 widens to form a narrowinner partial cylindrical surface 140. It is foreseen that in otherembodiments of the invention, the surface 140 may be radiused orotherwise curved, convex or concave. The discontinuous surfaces 130, 133and 140 are sized to advantageously frictionally engage the bone screwshank upper portion or head 8, allowing for an un-locked friction fit,non-floppy placement of the angle of the shank 4 with respect to thereceiver 10 during surgery prior to locking of the shank 4 with respectto the receiver 10 near the end of the procedure. In the lockedposition, depending upon the angular orientation of the shank head 8,the surfaces and or edges 133 do not substantially engage the shank head8. The discontinuous cupped surface 138 that is located on either sideof the slit 136 and is substantially formed in the bottom surface 124,the frusto-conical surface 128 and the inner concave radiused surface132, is positioned, sized and shaped to eventually cooperate with thecupped surface 109 of the receiver 10, allowing for an increased angularorientation of the shank 4 with respect to the receiver 10 as will bedescribed in greater detail below.

The retainer body 116 has an outer substantially cylindrical profiledefined by an outer cylindrical surface 142 sized and shaped to closelyand slidingly fit within the receiver cavity 61. Formed in the surface142 is one or more vertically extending grooves 144, the illustratedembodiment has two grooves 144. As will be described with respect toFIGS. 47-54, more or fewer grooves at inner as well as outer surfaces ofthe retainer are shown in alternative embodiments of the retainer 12.

The opposed pair of spring tabs 118 extend outwardly away from oneanother and thus outwardly from the body 116 outer cylindrical surface142. Each spring tab 118 is sized and shaped to closely cooperate andfrictionally engage surfaces of the receiver 10 and the through bore 77as will be described in greater detail below. An outer surface 146 ofeach spring tab 118 located adjacent each upper surface 122 as well asan optional substantially horizontal elongate notch or grooved surface147 are sized and shaped to cooperate with and frictionally engage thereceiver inner arm surfaces, as shown, for example, in FIG. 35. Theouter surface 146 extends downwardly below the notched surface 147 to alocation at or near the body outer cylindrical surface 142. In theillustrated embodiment, an outer transition surface 148 spans betweenthe surface 146 and the surface 142. The notches 147 (which in someembodiments may be replaced by projections, multiple grooves or notchesof various geometries and orientations, for example), aid to resilientlyhold the retainer in an upper portion of the receiver cavity 61 whendesired, but also resiliently release when the retainer 12 is pressedinto a lower portion of the receiver cavity 61. The illustrated springtabs 118 each include one or more planar (as illustrated) or curvedconcave inner surfaces 149 running from the top surface 122 to a tabbase seat, surface or surfaces 150 located adjacent to the cylindricalinner surface 146 as well as the body top surfaces 134. The surfaces 149extend both outwardly and upwardly from the base seat surfaces 150. Itis foreseen that in other embodiments of the invention, fewer or greaternumber of planar or other surfaces with other geometries may extendbetween the top surface 122 and the inner surfaces defining the body 116of the retainer 12.

The through slit 136 of the resilient retainer 12 is defined by firstand second end surfaces, 152 and 153 disposed in spaced relation to oneanother (they may also be touching) when the retainer is in a neutral ornominal state. Both end surfaces 152 and 153 are disposed at an anglewith respect to the bottom surface 124. A width X between the surfaces152 and 153 is very narrow (slit may be made by EDM process) to providestability to the retainer 12 during operation. Because the retainer 12is top loadable in a neutral state and the retainer 12 does not need tobe compressed to fit within the receiver cavity 61 at the cylindricalsurface 99, the width X may be much smaller than might be required for abottom loaded compressible retainer ring. The initial gap X of theretainer 12 prior to attachment to the shank head 8 functions only inexpansion to allow the retainer 12 to expand about the shank head 8.This results in a stronger retainer that provides more surface contactwith the shank upper portion 8 upon locking, resulting in a sturdierconnection with less likelihood of failure than a retainer ring having agreater gap. Furthermore, because the retainer 12 body 116 is onlyexpanded and never compressed inwardly beyond the initial neutral stateprior to assembly, the retainer 12 does not undergo the mechanicalstress that typically is placed on spring ring type retainers known inthe prior art that are both compressed inwardly and expanded outwardlyduring assembly. It has been found that once the retainer 12 is expandedabout the shank head 8, the retainer 12 may return to a new nominal orneutral orientation in which a gap between the surfaces 152 and 153 isslightly greater than the gap X. As will be described in greater detailbelow, the assembly 1 advantageously provides for access to the insert14 and the retainer 12 to allow for pressing of the retainer 12 downonto the receiver seat portion 104 and reducing the retainer 12 into thereceiver 10 inner cylindrical surface 101 as desired, prior to lockingof the assembly 1 with a rod and closure top.

With particular reference to FIGS. 1 and 18-23, the compression insert14 is illustrated that is sized and shaped to be received by anddown-loaded into the receiver 10 at the upper opening 66. Thecompression insert 14 has an operational central axis that is the sameas the central axis B of the receiver 10. In operation, the insertadvantageously frictionally engages the bone screw shank upper portion8. As will be described in greater detail below with respect to thealternative insert 214 shown in FIGS. 55-58, in some embodiments of theinvention, the insert that has locked the shank 4 in a desired angularposition with respect to the receiver 10, by, for example, compressionfrom the rod 21 and closure top 18, is also forced into an interferencefit engagement with the receiver 10 at an outer surface thereof and thusis capable of retaining the shank 6 in a locked position even if the rod21 and closure top 18 are removed. Such locked position may also bereleased by the surgeon if desired. The non-locking insert 14 as well asthe locking insert 214 are preferably made from a solid resilientmaterial, such as a stainless steel or titanium alloy, so that portionsof the insert may be pinched or pressed, if necessary, and un-wedgedfrom the receiver 10 with a release tool.

The non-locking compression insert 14 includes a substantiallycylindrical body 156 integral with a pair of upstanding arms 157.Extending outwardly from each arm 157 is an integral wing or extension158. A bore, generally 160, is disposed primarily within and through thebody 156 and communicates with a generally U-shaped through channelformed by a saddle 161 that is substantially defined by the upstandingarms 157. The saddle 161 has a lower seat 162 sized and shaped toclosely, snugly engage the rod 21. It is foreseen that an alternativeembodiment may be configured to include planar holding surfaces thatclosely hold a square or rectangular bar as well as hold a cylindricalrod-shaped, cord, or sleeved cord longitudinal connecting member. Thearms 157 disposed on either side of the channel extend upwardly andoutwardly from the body 156 and terminate at top surfaces 164. The arms157 are sized and configured for ultimate placement beneath thecylindrical run-out surface 92 located below the receiver guide andadvancement structure 72 with the wings 158 extending through thereceiver aperture 83 located below the arm surface 82. It is foreseenthat in some embodiments of the invention, the arms may be extendedupwardly and the closure top configured such that the arms and, morespecifically, the surfaces 164 ultimately directly engage the closuretop 18 for locking of the polyaxial mechanism, for example, when the rod21 is made from a deformable material. In such embodiments, the insert14 would include a rotation blocking structure or feature that abutsagainst cooperating structure located on an inner wall of the receiver10, preventing rotation of the insert with respect to the receiver whenthe closure top is rotated into engagement with the insert. In thepresent embodiment, the arms 157 include upper outer cylindricalsurfaces 163 located below the wings 158 and the top surfaces 164, thesurfaces 163 located within the receiver arm cylindrical surfaces 95 andthe top surfaces 164 being ultimately positioned in spaced relation withthe closure top 18, so that the closure top 18 frictionally engages therod 21 only, pressing the rod 21 downwardly against the seating surface162, the insert 14 in turn pressing against the shank 4 upper portion 8that presses against the retainer 12 to lock the polyaxial mechanism ofthe bone screw assembly 1 at a desired angle. The wings 158 arepartially defined by the upper surfaces 164 and partially defined byouter partially cylindrical surfaces 165. The surfaces 165 are sized andshaped for rotation within the receiver arm cylindrical surfaces 92during assembly of the insert 14 with the receiver 10 as will bedescribed in greater detail below.

The bore, generally 160, is substantially defined at the body 156 by aninner cylindrical surface 166 that communicates with the seat 162 and alower concave substantially spherical surface 168 having a radius thesame or substantially similar to a radius of the surface 34 of the shankupper portion 8. The surface 168 terminates at an annular edge or rimbase surface 169 of the body 156. Located between the cylindricalsurface 166 and the spherical surface 168 or located along the sphericalsurface 168 is a shank gripping surface portion, generally 170. Thegripping surface portion 170 includes one or more stepped surfaces orridges sized and shaped to grip and penetrate into the shank head 8 whenthe insert 14 is locked against the head surface 34. It is foreseen thatthe stepped surface portion 170 may include greater or fewer number ofstepped surfaces. It is foreseen that the shank gripping surface portion170 and also the spherical surface 168 may additionally or alternativelyinclude a roughened or textured surface or surface finish, or may bescored, knurled, or the like, for enhancing frictional engagement withthe shank upper portion 8.

The compression insert 14 through bore 160 is sized and shaped toreceive the driving tool (not shown) therethrough that engages the shankdrive feature 46 when the shank body 6 is driven into bone with thereceiver 10 attached. Also, in some locking embodiments of theinvention, the bore receives a manipulation tool (not shown) used forreleasing the insert from a locked position with the receiver, the toolpressing down on the shank and also gripping the insert at through boreslocated in the arms or with other tool engaging features. For example, amanipulation tool for releasing the insert from the receiver 10 may alsoaccess such bores from the receiver through the apertures in thereceiver. Thereby, tools can be configured to release a locking insertfrom the inside and outside of the receiver 10.

The illustrated insert 14 further includes a lower, planar outer armsurface 173 adjacent to the bottom rim 169 and an outer middle armsurface 174 located between the arm surface 164 and the lower surface173. The surface 174 is recessed from the surface 164 and the surface173 is recessed from the surface 174, giving the insert 14 arms aninwardly and downwardly stepped profile running from the top surfaces164 to the bottom rim surface 169. The surface 174 is cylindrical, butin some embodiments may be planar or of another curved shape. Located ateither side of the wings 158 and the arm surfaces 163 are verticallyextending grooves or squared-off surface portions or notches 175A and175B that run from the respective top surface 164 to the respectivelower arm surface 174. The grooves 175A and 175B cooperate with thereceiver crimp walls 86 and 87 to aid in alignment of the insert channelor saddle 161 with the receiver channel 64. Spanning between each armsurface 174 and each arm surface 173 is a sloping surface 178 that formsa ledge for cooperation with the retainer spring tabs 118, the surface178 forming an oblique angle with the insert central axis. In someembodiments of the invention, the entire ledge is substantiallyperpendicular to the central axis of the insert 14. In the illustratedembodiment, the sloping outer ledge surface 178 is integral with aninner surface 179 that is substantially perpendicular to the centralaxis of the insert 14, the surface 179 located near or adjacent the armsurface 173. In the illustrated embodiment and curved transition surface180 provides a rounded off corner connection between the surface 179 andthe arm surface 173. The surfaces 179 abut against the retainer 12spring tab top surfaces 122 during some of the early stages of assemblybetween the insert 14, the retainer 12 and the receiver 10, while thesurfaces 178 provide adequate clearance for the retainer spring tabs 118during later stages of assembly as will be described in greater detailbelow. Each of the arms 157 and the insert body 156 may include moresurface features, such as cut-outs notches, bevels, etc. to provideadequate clearance for inserting the insert 14 into the receiver andcooperating with the retainer 12 during the different assembly steps aswill be described in greater detail below.

The insert body 156 has an outer diameter slightly smaller than adiameter between crests of the guide and advancement structure 72 of thereceiver 10, allowing for top loading of the compression insert 14 intothe receiver opening 66, with the arms 157 of the insert 14 beinglocated between the receiver arms 62 during insertion of the insert 14into the receiver 10. Once the arms 157 of the insert 14 are generallylocated beneath the guide and advancement structure 72, the insert 14 isrotated in a clockwise direction into place about the receiver axis Buntil the wings 158 are located in the apertures 83 as will be describedin greater detail below

With reference to FIGS. 1 and 39-46, the illustrated elongate rod orlongitudinal connecting member 21 (of which only a portion has beenshown) can be any of a variety of implants utilized in reconstructivespinal surgery, but is typically a cylindrical, elongate structurehaving the outer substantially smooth, cylindrical surface 22 of uniformdiameter. The rod 21 may be made from a variety of metals, metal alloys,non-metals and deformable and less compressible plastics, including, butnot limited to rods made of elastomeric, polyetheretherketone (PEEK) andother types of materials, such as polycarbonate urethanes (PCU) andpolyethelenes.

Longitudinal connecting members for use with the assembly 1 may take avariety of shapes, including but not limited to rods or bars of oval,rectangular or other curved or polygonal cross-section. The shape of theinsert 14 may be modified so as to closely hold the particularlongitudinal connecting member used in the assembly 1. Some embodimentsof the assembly 1 may also be used with a tensioned cord. Such a cordmay be made from a variety of materials, including polyester or otherplastic fibers, strands or threads, such as polyethylene-terephthalate.Furthermore, the longitudinal connector may be a component of a longeroverall dynamic stabilization connecting member, with cylindrical orbar-shaped portions sized and shaped for being received by thecompression insert 14 of the receiver having a U-shaped, rectangular- orother-shaped channel, for closely receiving the longitudinal connectingmember. The longitudinal connecting member may be integral or otherwisefixed to a bendable or damping component that is sized and shaped to belocated between adjacent pairs of bone screw assemblies 1, for example.A damping component or bumper may be attached to the longitudinalconnecting member at one or both sides of the bone screw assembly 1. Arod or bar (or rod or bar component) of a longitudinal connecting membermay be made of a variety of materials ranging from deformable plasticsto hard metals, depending upon the desired application. Thus, bars androds of the invention may be made of materials including, but notlimited to metal and metal alloys including but not limited to stainlesssteel, titanium, titanium alloys and cobalt chrome; or other suitablematerials, including plastic polymers such as polyetheretherketone(PEEK), ultra-high-molecular weight-polyethylene (UHMWP), polyurethanesand composites, including composites containing carbon fiber, natural orsynthetic elastomers such as polyisoprene (natural rubber), andsynthetic polymers, copolymers, and thermoplastic elastomers, forexample, polyurethane elastomers such as polycarbonate-urethaneelastomers.

With reference to FIGS. 1 and 39-40, the closure structure or closuretop 18 shown with the assembly 1 is rotatably received between thespaced arms 62 of the receiver 10. It is noted that the closure 18 topcould be a twist-in or slide-in closure structure. The illustratedclosure structure 18 is substantially cylindrical and includes a anouter helically wound guide and advancement structure 182 in the form ofa flange that operably joins with the guide and advancement structure 72disposed on the arms 62 of the receiver 10. The flange form utilized inaccordance with the present invention may take a variety of forms,including those described in Applicant's U.S. Pat. No. 6,726,689, whichis incorporated herein by reference. Although it is foreseen that theclosure structure guide and advancement structure could alternatively bea buttress thread, a square thread, a reverse angle thread or otherthread like or non-thread like helically wound advancement structure,for operably guiding under rotation and advancing the closure structure18 downward between the arms 62 and having such a nature as to resistsplaying of the arms 62 when the closure structure 18 is advanced intothe channel 64, the flange form illustrated herein as described morefully in Applicant's U.S. Pat. No. 6,726,689 is preferred as the addedstrength provided by such flange form beneficially cooperates with andcounters any reduction in strength caused by the any reduced profile ofthe receiver 10 that may more advantageously engage longitudinalconnecting member components. The illustrated closure structure 18 alsoincludes a top surface 184 with an internal drive 186 in the form of anaperture that is illustrated as a star-shaped internal drive such asthat sold under the trademark TORX, or may be, for example, a hex drive,or other internal drives such as slotted, tri-wing, spanner, two or moreapertures of various shapes, and the like. A driving tool (not shown)sized and shaped for engagement with the internal drive 186 is used forboth rotatable engagement and, if needed, disengagement of the closure18 from the receiver arms 62. It is also foreseen that the closurestructure 18 may alternatively include a break-off head designed toallow such a head to break from a base of the closure at a preselectedtorque, for example, 70 to 140 inch pounds. Such a closure structurewould also include a base having an internal drive to be used forclosure removal. A base or bottom surface 188 of the closure is planarand further includes a point 189 and a rim 190 for engagement andpenetration into the surface 22 of the rod 21 in certain embodiments ofthe invention. It is noted that in some embodiments, the closure topbottom surface 188 does not include the point and/or the rim. Theclosure top 18 may further include a cannulation through bore (notshown) extending along a central axis thereof and through the top andbottom surfaces thereof. Such a through bore provides a passage throughthe closure 18 interior for a length of wire (not shown) insertedtherein to provide a guide for insertion of the closure top into thereceiver arms 62. An alternative closure top (not shown) for use with adeformable rod, such as a PEEK rod, for example, may include a domedlower surface in lieu of the point and rim surface of the closure top18.

The assembly 1 receiver 10, retainer 12 and compression insert 14 aretypically assembled at a factory setting that includes tooling forholding and alignment of the component pieces and pinching orcompressing of the retainer 12 spring tabs 118 and rotating andotherwise manipulating the insert 14 arms, as well as crimping a portionof the receiver 10 toward the insert 14. In some circumstances, theshank 4 is also assembled with the receiver 10, the retainer 12 and thecompression insert 14 at the factory. In other instances, it isdesirable to first implant the shank 4, followed by addition of thepre-assembled receiver, retainer and compression insert at the insertionpoint. In this way, the surgeon may advantageously and more easilyimplant and manipulate the shanks 4, distract or compress the vertebraewith the shanks and work around the shank upper portions or headswithout the cooperating receivers being in the way. In other instances,it is desirable for the surgical staff to pre-assemble a shank of adesired size and/or variety (e.g., surface treatment of roughening theupper portion 8 and/or hydroxyapatite on the shank 6), with thereceiver, retainer and compression insert. Allowing the surgeon tochoose the appropriately sized or treated shank 4 advantageously reducesinventory requirements, thus reducing overall cost and improvinglogistics and distribution.

Pre-assembly of the receiver 10, retainer 12 and compression insert 14is shown in FIGS. 24-31. With particular reference to FIG. 24, first theretainer 12 is inserted into the upper receiver opening 66, leading withone of the spring tabs 118 with both of the spring tab top surfaces 122facing one arm 62 and the retainer bottom surface 124 facing theopposing arm 62 (shown in phantom). The retainer 12 is then lowered insuch sideways manner into the channel 64 and partially into the receivercavity 61, followed by tilting the retainer 12 such that the top surface122 and thereafter the top surface 122 of the leading spring tab 118 istemporarily moved into a nearby receiver arm aperture 83. With referenceto FIG. 25, the retainer 12 is then further tilted or turned and thenmanipulated downwardly within the receiver as shown in phantom, thespring tabs 118 being compressed inwardly as the retainer is lowered toa position within the cavity as shown in solid lines in FIG. 25, theretainer 12 bottom surface 124 ultimately seating on the receiversurface 104 and the spring tabs 118 returning to a neutral state,extending into the apertures 77. To accomplish the tilting and turningof the retainer 12 required for ultimately seating the retainer on thereceive surface 104, the spring tab arm 118 may require some downwardand upward tilting, shifting in and out of the aperture 83 until thetabs are pressed resiliently inwardly towards one another at thereceiver surface 97 and finally allowed to spring outwardly at theapertures 77. At this time, the retainer 12 is captured within thereceiver base cavity 61 unless the spring tabs 118 are squeezed towardone another so as to clear the through apertures 77.

With reference to FIGS. 25-27, the compression insert 14 is thendownloaded into the receiver 10 through the upper opening 66 with thebottom surface 169 facing the receiver arm top surfaces 73 and theinsert arm wings 158 located between the opposed receiver arms 62. Theinsert 14 is then lowered toward the receiver base 60 until the insert14 arm upper surfaces 164 are adjacent the run-out area below the guideand advancement structure 72 defined in part by the cylindrical surface92. Thereafter, the insert 14 is rotated (see the arrow K in FIG. 27)about the receiver axis B until the upper arm surfaces 164 are directlybelow the guide and advancement structure 72 and the insert wings 158are extending through the receiver grooves 75 and into the apertures 83located below the receiver surfaces 82 as illustrated in FIGS. 28-30with the U-shaped channel 161 of the insert 14 aligned with the U-shapedchannel 64 of the receiver 10. In some embodiments, the insert arms 157may need to be compressed slightly during rotation to clear some of theinner surfaces 70 of the receiver arms 62. With particular reference toFIGS. 28 and 29, thereafter, the four receiver crimping walls or tabs 86and 87 are then pressed inwardly toward and against the respectiveinsert 14 v-notch or grooved surfaces 175A and 1758. The crimping walls86 and 87 help retain the desired alignment between the insert 14 andthe receiver 10 and prohibit relative rotation between the two parts.However, relative vertical movement between the insert 14 and thereceiver 10 is possible as the crimping walls do not vertically fix theinsert with respect to the receiver.

With particular reference to FIG. 30, a tool (not shown) is then used togrip the retainer spring tab arms 118 at outer surfaces 146, 148 thereofand squeeze or press the tabs 118 toward one another while moving theretainer 12 in an upward direction away from the surface 104 and near orinto engagement with the insert 14 at the surface 179. When the springtab surfaces 146 and outer grooves 147 are located within the receivercylindrical surfaces 95 and 97, the manipulation tool (not shown) isreleased and the retainer grooves 147 engage the surfaces 97 locateddirectly below the sloping ledge 96 as shown in FIG. 31. The resilientspring tabs 118 press against the surfaces 97, the portion of thesurfaces 97 now disposed within the retainer grooves 147 prohibitingdownward and upward movement of the retainer 12 within the receiver 10.The retainer 12 and the insert 14 are now in a desired position forshipping as an assembly along with the separate shank 4. The insert 14is also fully captured within the receiver 10 by the guide andadvancement structure 72 prohibiting movement of the insert 14 up andout through the receiver opening 66 as well as by retainer 12 locatedbelow the insert.

Typically, the receiver and retainer combination are shipped orotherwise provided to the end user with the spring tabs 118 wedgedagainst the receiver as shown in FIG. 31. The receiver 10, retainer 12and insert 14 combination is now pre-assembled and ready for assemblywith the shank 4 either at the factory, by surgery staff prior toimplantation, or directly upon an implanted shank 4 as will be describedherein.

As illustrated in FIG. 32, the bone screw shank 4 or an entire assembly1 made up of the assembled shank 4, receiver 10, retainer 12 andcompression insert 14, is screwed into a bone, such as the vertebra 17(shown in phantom), by rotation of the shank 4 using a suitable drivingtool (not shown) that operably drives and rotates the shank body 6 byengagement thereof at the internal drive 46. Specifically, the vertebra17 may be pre-drilled to minimize stressing the bone and have a guidewire (not shown) inserted therein to provide a guide for the placementand angle of the shank 4 with respect to the vertebra. A further taphole may be made using a tap with the guide wire as a guide. Then, thebone screw shank 4 or the entire assembly 1 is threaded onto the guidewire utilizing the cannulation bore 50 by first threading the wire intothe opening at the bottom 28 and then out of the top opening at thedrive feature 46. The shank 4 is then driven into the vertebra using thewire as a placement guide. It is foreseen that the shank and other bonescrew assembly parts, the rod 21 (also having a central lumen in someembodiments) and the closure top 18 (also with a central bore) can beinserted in a percutaneous or minimally invasive surgical manner,utilizing guide wires and attachable tower tools mating with thereceiver. When the shank 4 is driven into the vertebra 17 without theremainder of the assembly 1, the shank 4 may either be driven to adesired final location or may be driven to a location slightly above orproud to provide for ease in assembly with the pre-assembled receiver,compression insert and retainer.

With further reference to FIG. 32, the pre-assembled receiver, insertand retainer are placed above the shank upper portion 8 until the shankupper portion is received within the opening 110. With particularreference to FIGS. 32-35, as the shank upper portion 8 is moved into theinterior 61 of the receiver base, the shank upper portion 8 pressesupwardly against the retainer 12 in the receiver recess partiallydefined by the cylindrical surface 99. As the shank head 8 continues tomove upwardly toward the channel 64, the shank head surface 34 forcesoutward movement of the retainer 12 towards the cylindrical surface 99defining the receiver expansion recess or chamber as best shown in FIG.33, with the retainer spring tabs 118 remaining in an inwardly pressedposition at the grooves 147 that are captured at the receiver surfaces97. At this time, the spherical surface 34 of the head 8 is in contactwith the surface 130 of the retainer 12. FIG. 34 illustrates thewidening of the slit 136 defined by the surfaces 152 and 153 duringexpansion of the retainer 12 about the shank head 8. FIG. 34 alsoillustrates the position of the spring tabs 18 abutting against theinsert surfaces 178 and 179 during expansion of the retainer 12 aboutthe shank head 8, the head 8 hemisphere being shown in dotted lines.With reference to FIG. 35, the retainer 12 begins to return towards aneutral or nominal state as the center of the sphere of the head passesbeyond the retainer surface 130. At this time, the spherical surface 34moves into engagement with the inner upper rim surfaces 133 of theretainer 12 while the surface 34 remains in contact with at least anedge of the lower cylindrical surface 130. The combination of the rim133 surface contact and the lower surface 130 contact (that each definea terminal portion of the smaller radiused surface 132), bothresiliently pressing against the larger radiused surface 34, provides afairly tight friction fit between the head 8 and the retainer 12, thesurface 34 being pivotable with respect to the retainer 12 with someforce. Thus, a tight, non-floppy ball and socket joint is now createdbetween the retainer 12 and the shank upper portion 8.

With reference to FIG. 36, the receiver is then pulled upwardly or theshank 4 and attached retainer 12 are then moved manually downwardly intoa position wherein the retainer spring tab 118 grooves 147 aredisengaged from the receiver surfaces 97, allowing the tabs 118 toresiliently extend outwardly into a neutral or near-neutral position,slightly extending into each of the receiver through apertures 77. It isforeseen that in some embodiments of the invention, an upper portion ofthe aperture 77 may include a wall or a recessed surface may be formedin the receiver directly above the aperture 77, to provide for atemporary abutment surface for the spring tabs 118 during angularmanipulation of the shank with respect to the retainer and receiver, butprior to final locking of the shank with respect to the receiver, inorder to further increase the friction fit relationship between theshank and the retainer during surgery.

With further reference to FIGS. 36 and 37, after the retainer 12 ismoved downwardly into the receiver 10, the insert 14 also movesdownwardly into engagement with the retainer 12 (FIG. 37). However, atthis time, the retainer 12 may not yet be seated on the receiver seatingsurface 104. As shown in FIGS. 36 and 37, it has been found that theresilient retainer 12 may not return to an original nominal or neutralstate that the retainer 12 was in prior to expansion about the shankhead 8 and thus may be spaced from the receiver surface 104 and noteasily pressed into a desired seated position. In situations wherein theslit 136 of the retainer requires additional force to return to theoriginal pre-expansion state, a tool (not shown) having opposed prongsor arms is received in the opposed receiver slots or outer grooves 74and moved downwardly into abutment with the exposed top surfaces 164 ofthe insert wings 158. With reference to FIG. 38, the insert 14 at thesloping surfaces 178 is then pressed downwardly by such a tool intoengagement with inner surfaces 149 of the retainer spring tabs 118, andthe insert 14 and the retainer 12 may then be forced downwardly untilthe retainer bottom surface 124 abuts against the receiver seat 104, theretainer 12 being pressed inwardly along the sloping surface or surfaces102. At this time, the retainer spring tabs 118 are spread slightlyfurther outwardly into the receiver bores 77, making it impossible tomove the retainer out of the locking portion of the receiver chamberdefined in part by the receiver seat 104 unless pressed inwardly by atool or tools via the through bores 78. In some embodiments, when thereceiver 10 is pre-assembled with the shank 4, the entire assembly 1 maybe implanted at this time by inserting the driving tool (not shown) intothe receiver and the shank drive 46 and rotating and driving the shank 4into a desired location of the vertebra 17. With reference to FIG. 38and also, for example, to FIGS. 41-46, at this time, prior to lockingwith a closure top, the receiver 10 may be articulated to a desiredangular position with respect to the shank 4, such as that shown in FIG.54, that will be held, but not locked, by the frictional engagementbetween the retainer 12 and the shank upper portion 8. With furtherreference to FIG. 38 and also FIG. 39, the insert 14 may be presseddownwardly into locking engagement with the shank head 8 by a toolfurther pressing on the wings 158 as previously described herein or bythe rod 21 and the closure top 18.

With reference to FIGS. 39 and 40, the rod 21 is eventually positionedin an open or percutaneous manner in cooperation with the at least twobone screw assemblies 1. The closure structure 18 is then advancedbetween the arms 62 of each of the receivers 10. The closure structure18 is rotated, using a tool engaged with the inner drive 186 until aselected pressure is reached at which point the rod 21 engages theU-shaped seating surface 162 of the compression insert 14, furtherpressing the insert spherical surface 168 and stepped shank grippingsurfaces 170 against the shank spherical surface 34, the edges of thestepped surfaces 170 penetrating into the spherical surface 34 (see alsoFIGS. 43 and 45), pressing the shank upper portion 8 into lockedfrictional engagement with the retainer 12. Specifically, as the closurestructure 18 rotates and moves downwardly into the respective receiver10, the point 189 and rim 190 engage and penetrate the rod surface 22,the closure structure 18 pressing downwardly against and biasing the rod21 into compressive engagement with the insert 14 that urges the shankupper portion 8 toward the retainer 12 and into locking engagementtherewith, the retainer 12 frictionally abutting the surface 104 andpressing outwardly against the cylindrical surface 101. For example,about 80 to about 120 inch pounds of torque on the closure top may beapplied for fixing the bone screw shank 6 with respect to the receiver10. If disassembly if the assembly 1 is desired, such is accomplished inreverse order to the procedure described previously herein for assembly.

With reference to FIGS. 41-46, different angular or articulatedpositions of the shank 4 with respect to the receiver 10 are shown, somemaking full use of the aligned cooperating cut-out or cupped surfaces109 and 138 of the respective receiver 10 and retainer 12. For example,FIGS. 41 and 46 illustrate arrangements wherein the shank is pivoted ina direction away from the cooperating surfaces 109 and 138.Specifically, FIG. 41 illustrates a twenty-five degree caudadarticulation, while FIG. 46 illustrates a multi-planar articulation thatdoes not utilize the cupped surfaces for increased angulation. FIGS. 42and 43 represent a twenty-five degree medial articulation, while FIGS.44 and 45 show a forty degree medial articulation, illustrating eitherend of a wide range of angulations or articulations greater thantwenty-five degrees possible with bone screw assemblies of theinvention.

With reference to FIGS. 47-48, an alternative retainer 12A isillustrated for use with the shank 4, receiver 10, insert 14 closure top18 and rod 21 previously described herein. The retainer 12A is identicalto the retainer 12 with the exception that the retainer 12A does notinclude any vertically extending outer grooves 144.

With reference to FIGS. 49-50, an alternative retainer 12B isillustrated for use with the shank 4, receiver 10, insert 14 closure top18 and rod 21 previously described herein. The retainer 12BA isidentical to the retainer 12 with the exception that the retainer 12Bincludes only one outer vertically groove 144B located generallyopposite a slit 136B.

With reference to FIGS. 51-52, an alternative retainer 12C isillustrated for use with the shank 4, receiver 10, insert 14 closure top18 and rod 21 previously described herein. The retainer 12A is identicalto the retainer 12 with the exception that the retainer 12A does notinclude any vertically extending outer grooves 144. Rather, the retainer12C includes a plurality of inner notches 144C located at or near aninner rim or cylindrical surface 130C that is otherwise identical to theinner cylindrical surface 130 of the retainer 12.

With reference to FIGS. 53-54, an alternative retainer 12D isillustrated for use with the shank 4, receiver 10, insert 14 closure top18 and rod 21 previously described herein. The retainer 12D is identicalto the retainer 12 with the exception that the retainer 12D furtherincludes a pair of inner expansion relief cut-outs 154D located belowand at either side of each spring tab 118D. The cut-outs 154D are formedin tab lower 150D and extend into an inner spherical surface 132D thatis otherwise identical to the surface 132 of the retainer 12.

With reference to FIGS. 55-58, an alternative lock-and-releasecompression insert 214 is illustrated for use with the shank 4, receiver10, retainer 12, closure top 18 and rod 21 previously described herein.The insert 214 is substantially similar to the insert 14 previouslydescribed herein, having all the features of the insert 14 and furtherincluding the additional feature of an outer locking surface 374, sizedand shaped for a locking interference fit with a surface of thereceiver, such as the cylindrical surface 95, and opposed manipulationslots 380 for use during locking and unlocking of the insert 214 withrespect to the receiver surface 95.

Thus, the insert 214 includes the lower arm surface 374 that is similarto the arm surface 174 of the insert 14 with the exception that thecylindrical surface 374 is sized for a locking interference fit with thereceiver inner cylindrical surface. In other words, a diameter of thesurface 374 is sized large enough to require that the cylindricalsurface 374 must be forced into the cylindrical surface 95 (or otherreceiver surface) by a tool or tools or by the closure top 18 forcingthe rod 21 downwardly against the insert 214 with sufficient force tointerferingly lock the insert 214 into the receiver 10. The insert isotherwise assembled with the receiver 10, retainer 12, shank 4, rod 21and closure top 18 in a manner the same as previously described abovewith respect to the assembly 1, with the exception that the insert 214must be forced downwardly into a locking interference fit with thereceiver 10 when the shank 4 is locked in place, as compared to theeasily sliding relationship between the insert 14 and the receiver 10.For example, the surfaces 374 and 95 may be sized such that the insert214 is prohibited from moving any further downwardly at the beginning ofthe surface 95 unless forced downwardly by a locking tool or by theclosure top pressing downwardly on the rod that in turn pressesdownwardly on the insert 214. Once the insert 214 is locked against thereceiver, the closure top 18 may be loosened or removed and/or the rod21 may be adjusted and/or removed and the frictional engagement betweenthe insert 214 and the receiver 10 at the receiver surface 95 willremain locked in place, advantageously maintaining a locked angularposition of the shank 4 with respect to the receiver 10. At such time,another rod, such as the deformable rod and cooperating alternativeclosure top may be loaded onto the already locked-up assembly to resultin an alternative assembly.

If unlocking of the insert 214 with respect to the receiver 10 isdesired, a tool (not shown) may be inserted into the slots 380 and theinsert 14 may be pulled away from the receiver 10. Such a tool mayinclude a piston-like portion for pushing directly on the shank whilethe insert 14 is pulled away from the receiver. In other embodiments, orapplications where a rod and closure top are still engaged with thereceiver 10, a tool (not shown) may be used to engage and pull up on theinsert wings that extend through the receiver apertures 83. At suchtime, the shank 4 may be articulated with respect to the receiver 10,and the desired friction fit returns between the retainer 12 and theshank surface 34, so that an adjustable, but non-floppy relationshipstill exists between the shank 4 and the receiver 10. If furtherdisassembly if the assembly is desired, such is accomplished in reverseorder to the procedure described previously herein for the assembly 1.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. In a bone anchor, the improvement comprising: a) a shankhaving a body for fixation to a bone and an integral upper substantiallyspherical head; b) a receiver having a top portion and a receiver baseand an outer surface, the receiver top portion defining a first openchannel, the base defining a chamber and a lower opening, the chambercommunicating with both the channel and the lower opening, the topportion having a pair of opposed through apertures formed therein; c) aninsert disposed within the receiver, the insert having a curved surfacesized and shaped for frictional mating cooperation with the shank headand having a second open channel, the insert further having a pair ofoutwardly extending arm portions, each arm portion having an interiorsurface and each arm portion partially extending through one of theapertures of the receiver, an arm portion interior surface having agroove, the groove being engageable a first manipulation tool formovement of the insert both downwardly into contact with the shank head,upwardly away from the shank head, and rotational movement of theinsert; and d) a resilient open retainer having a retainer base, theretainer captured within the chamber and expandable about at least aportion of the shank head and wherein expansion-only locking engagementoccurs between the shank upper portion and the retainer base and betweenthe retainer base and the receiver.
 2. The improvement of claim 1wherein a pair of shallow grooves are formed in the outer surface of thereceiver, each groove communicating with a respective aperture, eachgroove extending from the respective aperture to a top surface of thetop portion of the receiver, each groove having a width for receiving asecond manipulation tool.
 3. The improvement of claim 1 wherein theinsert has an outer surface releasably frictionally locked against thereceiver.
 4. The improvement of claim 1 wherein the insert being rotatedinto a locked position above the retainer with the second channelaligned with the first channel by the first manipulation tool in thegroove on the interior surface of the insert.
 5. The improvement ofclaim 4 wherein the insert outwardly extending arm portions are receivedby an inner cylindrical surface of the receiver top portion duringrotation of the insert with respect to the receiver.
 6. The improvementof claim 1 wherein the retainer base has at least a first planar surfaceseated on a second planar surface partially defining the receiverchamber.
 7. The improvement of claim 1 wherein the retainer base has afirst outer non-tapered surface in engagement with a second surfacepartially defining the receiver chamber.
 8. The improvement of claim 1wherein the retainer is partially defined by a concave inner partiallyspherical surface having a radius smaller than a radius of the shankhead and wherein at least one of an upper and a lower edge defining theretainer inner partially spherical surface is in frictional engagementwith the shank head.
 9. The improvement of claim 8 wherein both theupper and lower edges defining the retainer inner partially sphericalsurface are in temporary frictional engagement with the shank head toprovide a frictional but movable engagement between the shank head andthe retainer prior to locking of the shank head with respect to theretainer.
 10. The improvement of claim 1 wherein the retainer furthercomprises a pair of opposed outwardly extending resilient tabs and theretainer base has at least a first planar surface and the receiver has asecond planar surface partially defining the receiver chamber and asecond pair of opposed apertures and wherein after the shank head isreceived through the retainer base, the retainer base first planarsurface is seated on the receiver second surface and the resilient tabsexpand to a neutral state and are captured within the second pair ofreceiver apertures.
 11. The improvement of claim 1 wherein the receiverhas a cut-out along the opening of the base which creates a cuppedsurface.
 12. The improvement of claim 11 wherein the retainer has acut-out along the opening of the base which creates a cupped surface.13. In a bone anchor, the improvement comprising: a) a shank having abody for fixation to a bone and an integral upper substantiallyspherical head having a first radius; b) a receiver having a base, afirst pair of upright arms and an outer surface, the receiver uprightarms defining an open channel, the base defining a chamber and a loweropening, the chamber communicating with both the channel and the loweropening, each arm having a through aperture formed therein; c) an insertdisposed within the receiver chamber, the insert having a surface sizedand shaped for frictional mating cooperation with the shank head andhaving a second open channel, the insert further having a second pair ofupright arms, each arm having an interior surface and each arm having anoutwardly extending wing, the arm interior having a groove, the groovebeing engageable by a first manipulation tool for movement of the insertupward, downward, and rotationally; and d) a resilient open retainerhaving a base, the retainer captured within the chamber and expandableabout at least a portion of the shank head and wherein expansion-onlylocking engagement occurs between the shank upper portion and theretainer base and between the retainer base and the receiver, theretainer having a concave second substantially spherical surface with aradius smaller than the radius of the shank head, the second surfaceterminating at upper and lower edges, the edges temporarily frictionallymating with the shank head, providing a friction fit between theretainer and the shank head during non-locking angular manipulation ofthe shank with respect to the receiver.
 14. The improvement of claim 13wherein a pair of shallow grooves are formed in the outer surface of thereceiver, each groove communicating with a respective aperture, eachgroove extending from the respective aperture to a top surface of thetop portion of the receiver, each groove having a width for receiving asecond manipulation tool.
 15. The improvement of claim 13 wherein theinsert has an outer surface releasably frictionally locked against thereceiver.
 16. The improvement of claim 13 wherein the insert is toploaded into the receiver and then rotated by the first manipulation toolinto a position above the retainer with the insert second pair of armsaligned with the receiver first pair of arms and the wings locatedwithin the receiver apertures.
 17. The improvement of claim 13 whereinthe retainer base has at least a first planar surface seated on a secondplanar surface partially defining the receiver chamber.
 18. Theimprovement of claim 13 wherein the retainer base has a first outernon-tapered surface in engagement with a second surface partiallydefining the receiver chamber.
 19. The improvement of claim 13 whereinthe retainer further comprises a pair of opposed outwardly extendingresilient tabs and the retainer base having at least a first planarsurface and the receiver having a second planar surface partiallydefining the receiver chamber and a second pair of opposed apertures andwherein after the shank head is received through the retainer base, theretainer base first planar surface is seated on the receiver secondsurface and the resilient tabs expand to a neutral state and arecaptured within the second pair of receiver apertures.
 20. Theimprovement of claim 13 wherein the receiver has a cut-out along theopening of the receiver base which creates a cupped surface.
 21. Theimprovement of claim 20 wherein the retainer has a cut-out along theopening of the retainer base which creates a cupped surface.
 22. In abone anchor, the improvement comprising: a) a shank having a body forfixation to a bone and an integral upper portion having a convexsubstantially spherical first surface with a first radius; b) a receiverhaving a base and a pair of upright arms forming an open first channel,the base defining a chamber and having a lower opening, the channelcommunicating with the chamber; c) an insert disposed within thereceiver chamber having a second open channel with an interior surface,the interior surface having a groove that directly engages a lock andrelease tool; d) a resilient open retainer captured within the chamberand expandable about at least a portion of the shank upper portion, theretainer having a concave surface with a radius smaller than the radiusof the shank upper portion first surface, the retainer concave surfaceterminating at upper and lower edges, the edges frictionally mating withthe shank first spherical surface, providing a friction fit between theretainer and the shank during non-locking angular manipulation of theshank with respect to the receiver; and e) wherein expansion-onlylocking engagement occurs between the shank upper portion and theretainer and between the retainer and the receiver.
 23. The improvementof claim 22 wherein the receiver pair of upright arms is a first pair ofupright arms, and the insert comprises a body and a second pair ofupright arms, each insert arm having an outwardly extending wing, eachwing extending through an aperture of the receiver, the insert groovebeing engageable by the lock and release tool for movement of the insertupward, downward, and rotationally.
 24. The improvement of claim 23wherein a pair of shallow grooves are formed in the outer surface of thereceiver, each groove communicating with a respective receiver aperture,each groove extending from the respective aperture to a top surface ofthe receiver, each groove having a width for receiving a manipulationtool.
 25. The improvement of claim 22 wherein the retainer furthercomprises a pair of opposed outwardly extending resilient tabs and theretainer having a base with at least a first planar surface and thereceiver having a second planar surface partially defining the receiverchamber and a second pair of opposed apertures and wherein after theshank upper portion is received through the retainer base, the retainerbase first planar surface is seated on the receiver second surface andthe resilient tabs expand to a neutral state and are captured within thesecond pair of receiver apertures.
 26. The improvement of claim 22wherein the receiver has a cut-out along the opening of the receiverbase which creates a cupped surface.
 27. The improvement of claim 26wherein the retainer has a cut-out along the opening of the retainerbase which creates a cupped surface.